The present invention constitutes an improvement upon apparatus of the general type disclosed in Hodgson U.S. Pat. No. 4,056,226, issued Nov. 1, 1977. In particular, the improvement relates to slurry injecting apparatus which utilizes a slurry pump as in said patent, or a tank provided with air pressurizing means instead of a slurry pump.
A practical problem with slurry injectors of the type illustrated in U.S. Pat. No. 4,056,226 is that the several slurry delivery pipes which receive slurry from the wheeled tank through a common transverse manifold do not all deliver the same quantity of material per unit time under varying conditions of operation. The problem is rooted in the type of material that is handled in such slurry injectors. Most frequently the material is a blend of livestock manure and urine removed from animal holding areas, sometimes mixed with additional water and stored in large holding tanks with agitators to prevent fine solids from settling to the bottom of the tank as a sludge. The way in which such material is collected invariably causes it to include large debris such as pebbles, clods, sticks, and the like.
The injector pipes must be large enough that they will not become clogged with debris, and in practice it has been necessary to use injector pipes which are large enough that they cannot maintain a positive pressure head in the manifold. The slurry runs freely through the injector pipes into the ground. As a result, when the apparatus is operating on a sidehill so that one end of the manifold is lower than the other, the injector pipes toward the lower end of the manifold receive and deliver substantially more slurry than do the pipes toward the upper end of the manifold.
A slurry injector is intended to deliver moderate amounts of slurry to all the furrows in which the injector pipes operate, but it is entirely possible in sidehill operation to overflow the furrow or furrows toward the downhill side while providing little or no slurry to the furrows on the uphill side. Excessive concentration of the high nitrogen slurry can produce crop damage of one kind, while lack of sufficient slurry can produce another kind of crop damage.